Patent application title: CONVERTER CIRCUIT FOR SWITCHING A LARGE NUMBER OF SWITCHING VOLTAGE LEVELS

Abstract:

A converter circuit for switching a large number of switching voltage
levels is specified, in which a first switching group is provided for
each. Second switching groups are provided, each having a first, second,
third, fourth, fifth and sixth drivable bidirectional power semiconductor
switch and capacitor. The first drivable bidirectional power
semiconductor switch is reverse-connected in series with the second
drivable bidirectional power semiconductor switch, the third drivable
bidirectional power semiconductor switch is reverse-connected in series
with the fourth drivable bidirectional power semiconductor switch, the
first drivable bidirectional power semiconductor switch is connected to
the capacitor, the third drivable bidirectional power semiconductor
switch is connected to the capacitor, the fifth drivable bidirectional
power semiconductor switch is directly connected to the fourth drivable
bidirectional power semiconductor switch, and the sixth drivable
bidirectional power semiconductor switch is directly connected to the
second drivable bidirectional power semiconductor switch.

Claims:

1. A converter circuit for switching a large number of switching voltage
levels, comprising a first switching group provided for each phase
wherein the first switching group is formed by a first drivable
bidirectional power semiconductor switch and a second drivable
bidirectional power semiconductor switch and the first and the second
drivable bidirectional power semiconductor switches of the first
switching group are connected to one another, whereinn second switching
groups are provided, each having a first, second, third, fourth, fifth
and sixth drivable bidirectional power semiconductor switch and a
capacitor, wherein n≧1 and the first drivable bidirectional power
semiconductor switch is reverse-connected in series with the second
drivable bidirectional power semiconductor switch, the third drivable
bidirectional power semiconductor switch is reverse-connected in series
with the fourth drivable bidirectional power semiconductor switch, the
first drivable bidirectional power semiconductor switch is connected to
the capacitor, the third drivable bidirectional power semiconductor
switch is connected to the capacitor, the fifth drivable bidirectional
power semiconductor switch is directly connected to the fourth drivable
bidirectional power semiconductor switch and directly connected to the
junction point between the first drivable bidirectional power
semiconductor switch and the capacitor, and the sixth drivable
bidirectional power semiconductor switch is directly connected to the
second drivable bidirectional power semiconductor switch and directly
connected to the junction point between the third drivable bidirectional
power semiconductor switch and the capacitor, wherein,for n>1, each of
the n second switching groups is interlinked with the respective adjacent
second switching, whereinthe first switching group is connected to the
first second switching group, whereina third switching group and a fourth
switching group are provided, each having a first drivable bidirectional
power semiconductor switch, a second drivable bidirectional power
semiconductor switch, and a capacitor connected to the first and second
drivable bidirectional power semiconductor switches, wherein the first
and second drivable bidirectional power semiconductor switches are
connected to one another,in that the third switching group is connected
to the n-th second switching group, whereinthe fourth switching group is
connected to the n-th second switching group, and whereinthe third
switching group is connected to the fourth switching group.

2. A converter circuit for switching a large number of switching voltage
levels, comprising a first switching group provided for each phase
wherein the first switching group is formed by a first drivable
bidirectional power semiconductor switch and a second drivable
bidirectional power semiconductor switch and the first and the second
drivable bidirectional power semiconductor switches of the first
switching group are connected to one another, whereinn second switching
groups are provided, each having a first, second, third, fourth, fifth
and sixth drivable bidirectional power semiconductor switch and a
capacitor, wherein n≧1 and the first drivable bidirectional power
semiconductor switch is reverse-connected in series with the second
drivable bidirectional power semiconductor switch, the third drivable
bidirectional power semiconductor switch is reverse-connected in series
with the fourth drivable bidirectional power semiconductor switch, the
first drivable bidirectional power semiconductor switch is connected to
the capacitor, the third drivable bidirectional power semiconductor
switch is connected to the capacitor, the fifth drivable bidirectional
power semiconductor switch is directly connected to the fourth drivable
bidirectional power semiconductor switch and directly connected to the
junction point between the first drivable bidirectional power
semiconductor switch and the capacitor, and the sixth drivable
bidirectional power semiconductor switch is directly connected to the
second drivable bidirectional power semiconductor and directly connected
to the junction point between the third drivable bidirectional power
semiconductor switch and the capacitor, wherein,for n>1, each of the n
second switching groups is interlinked with the respective adjacent
second switching group, whereinthe first switching group is connected to
the first second switching group, whereina third switching group and a
fourth switching group are provided, each having a first drivable
bidirectional power semiconductor switch, a second drivable bidirectional
power semiconductor switch, and a capacitor connected to the first and
second drivable bidirectional power semiconductor switches, whereinthe
first and second drivable bidirectional power semiconductor switches are
connected to one another, whereinp fifth switching groups are provided,
each a first and a second drivable bidirectional power semiconductor
switch, wherein p>1, wherein,for p>1, each of the p fifth switching
groups is interlinked with the respective adjacent fifth switching group,
in that the first fifth switching group is connected to the n-th second
switching group, whereinthe third switching group is connected to the
p-th fifth switching group, whereinthe fourth switching group is
connected to the p-th fifth switching group, and whereinthe third
switching group is connected to the fourth switching group.

3. The converter circuit as claimed in claim 1, wherein the first drivable
bidirectional power semiconductor switch of the first switching group is
connected to the junction point between the first drivable bidirectional
power semiconductor switch and the capacitor of the first second
switching group, and the second power semiconductor switch of the first
switching group is connected to the junction point between the third
drivable bidirectional power semiconductor switch and the capacitor of
the first second switching group, whereinthe junction point between the
first drivable bidirectional power semiconductor switch and the second
drivable bidirectional power semiconductor switch of the third switching
group is connected to the junction point between the second drivable
bidirectional power semiconductor switch and the sixth drivable
bidirectional power semiconductor switch of the n-th second switching
group, whereinthe junction point between the first drivable bidirectional
power semiconductor switch and the second drivable bidirectional power
semiconductor switch of the fourth switching group is connected to the
junction point between the fourth drivable bidirectional power
semiconductor switch and the fifth drivable bidirectional power
semiconductor switch of the n-th second switching group, and whereinthe
capacitor of the third switching group is connected to the capacitor of
the fourth switching group.

4. The converter circuit as claimed in claim 1, wherein the first drivable
bidirectional power semiconductor switch of the first switching group is
connected to the junction point between the first drivable bidirectional
power semiconductor switch and the capacitor of the first second
switching group, and the second drivable bidirectional power
semiconductor switch of the first switching group is connected to the
junction point between the third drivable bidirectional power
semiconductor switch and the capacitor of the first second switching
group, whereinthe connection of the fifth drivable bidirectional power
semiconductor switch to the fourth drivable bidirectional power
semiconductor switch in the case of each second switching group is at the
junction point between the fourth drivable bidirectional power
semiconductor switch and the third drivable bidirectional power
semiconductor switch, and the connection of the sixth drivable
bidirectional power semiconductor switch to the second drivable
bidirectional power semiconductor switch in the case of each second
switching group is at the junction point between the second drivable
bidirectional power semiconductor switch and the first drivable
bidirectional power semiconductor switch, whereinthe junction point
between the first drivable bidirectional power semiconductor switch and
the second drivable bidirectional power semiconductor switch of the third
switching group is connected to the second drivable bidirectional power
semiconductor switch of the n-th second switching group, whereinthe
junction point between the first drivable bidirectional power
semiconductor switch and the second drivable bidirectional power
semiconductor switch of the fourth switching group is connected to the
fourth drivable bidirectional power semiconductor switch of the n-th
second switching group, and whereinthe capacitor of the third switching
group is connected to the capacitor of the fourth switching group.

5. The converter circuit as claimed in claim 2, wherein the first drivable
bidirectional power semiconductor switch of the first switching group is
connected to the junction point between the first drivable bidirectional
power semiconductor switch and the capacitor of the first second
switching group, and the second drivable bidirectional power
semiconductor switch of the first switching group is connected to the
junction point between the third drivable bidirectional power
semiconductor switch and the capacitor of the first second switching
group, whereinthe first drivable bidirectional power semiconductor switch
of the first fifth switching group is connected to the junction point
between the second drivable bidirectional power semiconductor switch and
the sixth drivable bidirectional power semiconductor switch of the n-th
second switching group, whereinthe second drivable bidirectional power
semiconductor switch of the first fifth switching group is connected to
the junction point between the fourth drivable bidirectional power
semiconductor switch and the fifth drivable bidirectional power
semiconductor switch of the n-th second switching group, whereinthe
junction point between the first drivable bidirectional power
semiconductor switch and the second drivable bidirectional power
semiconductor switch of the third switching group is connected to the
first drivable bidirectional power semiconductor switch of the p-th fifth
switching group, whereinthe junction point between the first drivable
bidirectional power semiconductor switch and the second drivable
bidirectional power semiconductor switch of the fourth switching group is
connected to the second drivable bidirectional power semiconductor switch
of the p-th fifth switching group, and whereinthe capacitor of the third
switching group is connected to the capacitor of the fourth switching
group.

6. The converter circuit as claimed in claim 2, wherein the first drivable
bidirectional power semiconductor switch of the first switching group is
connected to the junction point between the first drivable bidirectional
power semiconductor switch and the capacitor of the first second
switching group, and the second drivable bidirectional power
semiconductor switch of the first switching group is connected to the
junction point between the third drivable bidirectional power
semiconductor switch and the capacitor of the first second switching
group, whereinthe connection of the fifth drivable bidirectional power
semiconductor switch to the fourth drivable bidirectional power
semiconductor switch in the case of each second switching group is at the
junction point between the fourth drivable bidirectional power
semiconductor switch and the third drivable bidirectional power
semiconductor switch, and the connection of the sixth drivable
bidirectional power semiconductor switch to the second drivable
bidirectional power semiconductor switch in the case of each second
switching group is at the junction point between the second drivable
bidirectional power semiconductor switch and the first drivable
bidirectional power semiconductor switch, whereinthe first drivable
bidirectional power semiconductor switch of the first fifth switching
group is connected to the second drivable bidirectional power
semiconductor switch of the n-th second switching group, whereinthe
second drivable bidirectional power semiconductor switch of the first
fifth switching group is connected to the fourth drivable bidirectional
power semiconductor switch of the n-th second switching group, whereinthe
junction point between the first drivable bidirectional power
semiconductor switch and the second drivable bidirectional power
semiconductor switch of the third switching group is connected to the
first drivable bidirectional power semiconductor switch of the p-th fifth
switching group, whereinthe junction point between the first drivable
bidirectional power semiconductor switch and the second drivable
bidirectional power semiconductor switch of the fourth switching group is
connected to the second drivable bidirectional power semiconductor switch
of the p-th fifth switching group, and whereinthe capacitor of the third
switching group is connected to the capacitor of the fourth switching
group.

7. The converter circuit as claimed in claim 5, wherein each fifth
switching group has a capacitor connected to the first and second
drivable 3 o bidirectional power semiconductor switches of the associated
fifth switching group, whereinthe capacitor of the first fifth switching
group is connected to the junction point between the first drivable
bidirectional power semiconductor switch of the first fifth switching
group and the junction point between the second drivable bidirectional
power semiconductor switch and the sixth drivable bidirectional power
semiconductor switch of n-th second switching group, and whereinthe
capacitor of the first fifth switching group is connected to the junction
point between the second drivable bidirectional power semiconductor
switch of the first fifth switching group and the junction point between
the fourth drivable bidirectional power semiconductor switch and the
fifth drivable bidirectional power semiconductor switch of the n-th
second switching group.

8. The converter circuit as claimed in claim 6, wherein each fifth
switching group has a capacitor connected to the first and second
drivable bidirectional power semiconductor switches of the associated
fifth switching group, whereinthe capacitor of the first fifth switching
group is connected to the junction point between the first drivable
bidirectional power semiconductor switch of the first fifth switching
group and the second drivable bidirectional power semiconductor of the
n-th second switching group, and whereinthe capacitor of the first fifth
switching group is connected to the junction point between the second
drivable bidirectional power semiconductor switch of the first fifth
switching group and the fourth drivable bidirectional power semiconductor
switch of the n-th second switching group.

9. The converter circuit as claimed in claim 6, wherein the first fifth
switching group has a capacitor connected to the first and second
drivable bidirectional power semiconductor switches of the first fifth
switching group, whereinthe capacitor of the first fifth switching group
is connected to the junction point between the first drivable
bidirectional power semiconductor switch of the first fifth switching
group and the second drivable bidirectional power semiconductor switch of
the n-th second switching group, and whereinthe capacitor of the first
fifth switching group is connected to the junction point between the
second drivable bidirectional power semiconductor switch of the first
fifth switching group and the fourth drivable bidirectional power
semiconductor switch of the n-th second switching group.

10. The converter circuit as claimed in claim 6, wherein the first fifth
switching group and at least one further fifth switching group each have
a capacitor connected to the first and second drivable bidirectional
power semiconductor switches of the associated fifth switching,
whereinthe of the first fifth switching group is connected to the
junction point between the first drivable bidirectional power
semiconductor switch of the first fifth switching group and the second
drivable bidirectional power semiconductor switch of the n-th second
switching group, and whereinthe capacitor of the first fifth switching
group is connected to the junction point between the second drivable
bidirectional power semiconductor switch of the first fifth switching
group and the fourth drivable bidirectional power semiconductor switch of
the n-th second switching group.

11. The converter circuit as claimed in claim 1, wherein the first,
second, third, fourth, fifth and sixth drivable bidirectional power
semiconductor switches of each second switching group each has at least
two drivable bidirectional switching elements, wherein the drivable
bidirectional switching elements are connected in series.

12. The converter circuit as claimed in claim 1, wherein the first and
second drivable bidirectional power semiconductor switches of each fifth
switching group each have at least two drivable bidirectional switching
elements, wherein the drivable bidirectional switching elements are
connected in series.

13. The converter circuit as claimed in claim 1, wherein the first and
second drivable bidirectional power semiconductor switches of the third
switching group and the first and second drivable bidirectional power
semiconductor switches of the fourth switching group each have at least
two drivable bidirectional switching elements, wherein the drivable
bidirectional switching elements are connected in series.

14. The converter circuit as claimed in claim 10, wherein the first,
second, third, fourth, fifth and sixth drivable bidirectional power
semiconductor switches of each second switching group each has at least
two drivable bidirectional switching elements, wherein the drivable
bidirectional switching elements are connected in series.

15. The converter circuit as claimed in claim 11, wherein the first and
second drivable bidirectional power semiconductor switches of each fifth
switching group each have at least two drivable bidirectional switching
elements, wherein the drivable bidirectional switching elements are
connected in series.

16. The converter circuit as claimed in claim 13, wherein the first and
second drivable bidirectional power semiconductor switches of the third
switching group and the first and second drivable bidirectional power
semiconductor switches of the fourth switching group each have at least
two drivable bidirectional switching elements, wherein the drivable
bidirectional switching elements are connected in series.

Description:

RELATED APPLICATIONS

[0001]This application claims priority under 35 U.S.C. §119 to EP
Application 06405441.4 filed in Europe on Oct. 18, 2006, and as a
continuation application under 35 U.S.C. §120 to PCT/EP2007/060758
filed as an International Application on Oct. 10, 2007 designating the
U.S., the entire contents of which are hereby incorporated by reference
in their entireties.

TECHNICAL FIELD

[0002]The disclosure relates to the field of power electronics. It is
based on a converter circuit for switching a large number of switching
voltage levels.

BACKGROUND INFORMATION

[0003]Converter circuits are used nowadays in a wealth of power electronic
applications. The requirements made of such a converter circuit here
include, firstly, generating harmonics as little as possible on phases of
an electrical AC voltage system conventionally connected to the converter
circuit and, secondly, transmitting the largest possible powers with a
smallest possible number of electronic components. A suitable converter
circuit for switching a large number of switching voltage levels is
specified in DE 692 05 413 T2, wherein a first switching group and n
further first switching groups are provided for each phase, wherein
n≧1 and the first switching group is formed by a first drivable
bidirectional power semiconductor switch and a second drivable
bidirectional power semiconductor switch and the n further first
switching groups are each formed by a first drivable bidirectional power
semiconductor switch and a second drivable bidirectional power
semiconductor switch and by a capacitor connected to the first and second
drivable bidirectional power semiconductor switches. Each of the first
switching groups is connected in interlinked fashion to the respective
adjacent first switching group, wherein the first and the second drivable
bidirectional power semiconductor switch of the first further first
switching group are connected to one another. The first and the second
drivable bidirectional power semiconductor switches are each formed by a
bipolar transistor having a drive electrode arranged in insulated fashion
(IGBT--Insulated Gate Bipolar Transistor), and by a diode
reverse-connected in parallel with the bipolar transistor.

[0004]A further generic converter circuit for switching a large number of
switching voltage levels is specified in WO 2006/053448 A1.

[0005]What is problematic about a converter circuit for switching a large
number of switching voltage levels according to DE 692 05 413 T2 is that
the electrical energy stored in the converter circuit during operation is
very high. Since the electrical energy is stored in the capacitors of the
n first switching groups of the converter circuit, the capacitors have to
be designed for this electrical energy, that is to say with regard to
their dielectric strength and/or their capacitance. However, this
necessitates capacitors having a large structural size, which are
correspondingly expensive. Moreover, the converter circuit requires a
large amount of space on account of the capacitors that are large with
regard to the structural size, with the result that a space-saving
construction such as is required for many applications, for example for
traction applications, is not possible. Furthermore, the use of the
capacitors that are large with regard to the structural size brings about
a high mounting and maintenance outlay. Furthermore, the converter
circuit for switching a large number of switching voltage levels
according to DE 692 05 413 T2, on account of the exclusive use of bipolar
transistors having a drive electrode arranged in insulated fashion as
drivable power semiconductor switches, is susceptible to high voltages,
in particular to overvoltages, and additionally has considerable active
power losses.

SUMMARY

[0006]Exemplary embodiments disclosed herein are directed to a converter
circuit for switching a large number of switching voltage levels which
stores as little electrical energy as possible during its operation, can
be realized in space-saving fashion, is to the greatest possible extent
insensitive to high voltages and fault states and has low active power
losses.

[0007]A converter circuit for switching a large number of switching
voltage levels is disclosed, comprising a first switching group provided
for each phase wherein the first switching group is formed by a first
drivable bidirectional power semiconductor switch and a second drivable
bidirectional power semiconductor switch and the first and the second
drivable bidirectional power semiconductor switches of the first
switching group are connected to one another, wherein n second switching
groups are provided, each having a first, second, third, fourth, fifth
and sixth drivable bidirectional power semiconductor switch and a
capacitor, wherein n≧1 and the first drivable bidirectional power
semiconductor switch is reverse-connected in series with the second
drivable bidirectional power semiconductor switch, the third drivable
bidirectional power semiconductor switch is reverse-connected in series
with the fourth drivable bidirectional power semiconductor switch, the
first drivable bidirectional power semiconductor switch is connected to
the capacitor, the third drivable bidirectional power semiconductor
switch is connected to the capacitor, the fifth drivable bidirectional
power semiconductor switch is directly connected to the fourth drivable
bidirectional power semiconductor switch and directly connected to the
junction point between the first drivable bidirectional power
semiconductor switch and the capacitor, and the sixth drivable
bidirectional power semiconductor switch is directly connected to the
second drivable bidirectional power semiconductor switch and directly
connected to the junction point between the third drivable bidirectional
power semiconductor switch and the capacitor, wherein, for n>1, each
of the n second switching groups is interlinked with the respective
adjacent second switching, wherein the first switching group is connected
to the first second switching group, wherein a third switching group and
a fourth switching group are provided, each having a first drivable
bidirectional power semiconductor switch, a second drivable bidirectional
power semiconductor switch, and a capacitor connected to the first and
second drivable bidirectional power semiconductor switches, wherein the
first and second drivable bidirectional power semiconductor switches are
connected to one another, wherein the third switching group is connected
to the n-th second switching group, wherein the fourth switching group is
connected to the n-th second switching group, and wherein the third
switching group is connected to the fourth switching group.

[0008]A converter circuit for switching a large number of switching
voltage levels is disclosed, comprising a first switching group provided
for each phase wherein the first switching group is formed by a first
drivable bidirectional power semiconductor switch and a second drivable
bidirectional power semiconductor switch and the first and the second
drivable bidirectional power semiconductor switches of the first
switching group are connected to one another, wherein n second switching
groups are provided, each having a first, second, third, fourth, fifth
and sixth drivable bidirectional power semiconductor switch and a
capacitor, wherein n≧1 and the first drivable bidirectional power
semiconductor switch is reverse-connected in series with the second
drivable bidirectional power semiconductor switch, the third drivable
bidirectional power semiconductor switch is reverse-connected in series
with the fourth drivable bidirectional power semiconductor switch, the
first drivable bidirectional power semiconductor switch is connected to
the capacitor, the third drivable bidirectional power semiconductor
switch is connected to the capacitor, the fifth drivable bidirectional
power semiconductor switch is directly connected to the fourth drivable
bidirectional power semiconductor switch and directly connected to the
junction point between the first drivable bidirectional power
semiconductor switch and the capacitor, and the sixth drivable
bidirectional power semiconductor switch is directly connected to the
second drivable bidirectional power semiconductor and directly connected
to the junction point between the third drivable bidirectional power
semiconductor switch and the capacitor, wherein, for n>1, each of the
n second switching groups is interlinked with the respective adjacent
second switching group, wherein the first switching group is connected to
the first second switching group, wherein a third switching group and a
fourth switching group are provided, each having a first drivable
bidirectional power semiconductor switch, a second drivable bidirectional
power semiconductor switch, and a capacitor connected to the first and
second drivable bidirectional power semiconductor switches, wherein the
first and second drivable bidirectional power semiconductor switches are
connected to one another, wherein p fifth switching groups are provided,
each a first and a second drivable bidirectional power semiconductor
switch, wherein p>1, wherein, for p>1, each of the p fifth
switching groups is interlinked with the respective adjacent fifth
switching group, in that the first fifth switching group is connected to
the n-th second switching group, wherein the third switching group is
connected to the p-th fifth switching group, wherein the fourth switching
group is connected to the p-th fifth switching group, and wherein the
third switching group is connected to the fourth switching group.

[0009]These and further objects, advantages and features of the present
disclosure will become apparent from the following detailed description
of exemplary embodiments of the disclosure in conjunction with the
drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]In the figures:

[0011]FIG. 1 shows a first exemplary embodiment of a converter circuit
according to the disclosure,

[0012]FIG. 2 shows a second exemplary embodiment of a converter circuit
according to the disclosure,

[0013]FIG. 3 shows a third exemplary embodiment of a converter circuit
according to the disclosure,

[0014]FIG. 4 shows a fourth exemplary embodiment of a converter circuit
according to the disclosure,

[0015]FIG. 5 shows a fifth exemplary embodiment of a converter circuit
according to the disclosure,

[0016]FIG. 6 shows a sixth exemplary embodiment of a converter circuit
according to the disclosure, and

[0017]FIG. 7 shows a seventh exemplary embodiment of a converter circuit
according to the disclosure.

[0018]The reference symbols used in the drawing, and their meanings, are
summarized in the List of reference symbols. In principle, identical
parts are provided with identical reference symbols in the figures. The
exemplary embodiments described represent the subject matter of the
disclosure by way of example and have no restrictive effect.

DETAILED DESCRIPTION

[0019]The converter circuit according to the disclosure for switching a
large number of switching voltage levels comprises a first switching
group provided for each phase wherein the first switching group is formed
by a first drivable bidirectional power semiconductor switch and a second
drivable bidirectional power semiconductor switch and the first and the
second drivable bidirectional power semiconductor switches of the first
switching group are connected to one another. According to the
disclosure, n second switching groups are now provided, each having a
first, second, third, fourth, fifth and sixth drivable bidirectional
power semiconductor switch and capacitor, wherein n≧1 and the
first drivable bidirectional power semiconductor switch is
reverse-connected in series with the second drivable bidirectional power
semiconductor switch, the third drivable bidirectional power
semiconductor switch is reverse-connected in series with the fourth
drivable bidirectional power semiconductor switch, the first drivable
bidirectional power semiconductor switch is connected to the capacitor,
the third drivable bidirectional power semiconductor switch is connected
to the capacitor, the fifth drivable bidirectional power semiconductor
switch is directly connected to the fourth drivable bidirectional power
semiconductor switch and directly connected to the junction point between
the first drivable bidirectional power semiconductor switch and the
capacitor, and the sixth drivable bidirectional power semiconductor
switch is directly connected to the second drivable bidirectional power
semiconductor switch and directly connected to the junction point between
the third drivable bidirectional power semiconductor switch and the
capacitor. Furthermore, for n>1, each of the n second switching groups
is interlinked with the respective adjacent second switching group, and
the first switching group is connected to the first second switching
group. Furthermore, a third switching group and a fourth switching group
are provided, each having a first drivable bidirectional power
semiconductor switch, a second drivable bidirectional power semiconductor
switch, and a capacitor connected to the first and second drivable
bidirectional power semiconductor switches, wherein the first and second
drivable bidirectional power semiconductor switches are connected to one
another. The third switching group is connected to the n-th second
switching group, the fourth switching group is connected to the n-th
second switching group, and the third switching group is connected to the
fourth switching group. As an alternative, p fifth switching groups are
provided, each having a first and a second drivable bidirectional power
semiconductor switch, wherein p≧1 and, for p>1, each of the p
fifth switching groups is interlinked with the respective adjacent fifth
switching group. The first fifth switching group is then connected to the
n-th second switching group, the third switching group is connected to
the p-th fifth switching group, the fourth switching group is connected
to the p-th fifth switching group, and the third switching group is
connected to the fourth switching group. The p fifth switching groups
advantageously produce additional redundancy with regard to the drivable
bidirectional power semiconductor switches of the converter circuit
according to the disclosure.

[0020]Given an identical number of switching voltage levels, the converter
circuit according to the disclosure, by means of the n second switching
groups provided and by means of the third and fourth switching groups and
also by means of the p fifth switching groups and their connections
described above, can advantageously result in the number of capacitors of
the converter circuit being reduced in comparison with converter circuits
according to the prior art and, moreover, in the stored electrical energy
of the converter circuit being reduced. Consequently, the stored
electrical energy of the converter circuit can be kept small overall,
whereby the capacitors of the converter circuit only have to be designed
for a small electrical energy to be stored, that is to say with regard to
their dielectric strength and/or their capacitance. On account of the
resultant small structural size of the capacitors, the converter circuit
requires very little space, with the result that a space-saving
construction such as is required for many applications, for example for
traction applications, is advantageously possible. Moreover, the mounting
and maintenance outlay can also advantageously be kept small as a result
of the small structural size of the capacitors.

[0021]FIG. 1 shows an, in particular single-phase, first exemplary
embodiment of a converter circuit according to the disclosure for
switching a large number of switching voltage levels, wherein the
converter circuit comprises a first switching group 1 provided for each
phase R, S, T, wherein the first switching group 1 is formed by a first
drivable bidirectional power semiconductor switch 2 and a second drivable
bidirectional power semiconductor switch 3, and the first and the second
drivable bidirectional power semiconductor switches 2, 3 of the first
switching group 1 are connected to one another. The junction point
between the first and the second drivable bidirectional power
semiconductor switches 2, 3 of the first switching group 1 forms a phase
connection, in particular for the phase R, in accordance with FIG. 1.

[0022]According to the disclosure, now n second switching groups 4.1, . .
. 4.n are provided, each having a first, second, third, fourth, fifth and
sixth drivable bidirectional power semiconductor switch 5, 6, 7, 8, 9, 10
and a capacitor 11, wherein n≧1 and the first drivable
bidirectional power semiconductor switch 5 is reverse-connected in series
with the second drivable bidirectional power semiconductor switch 6, the
third drivable bidirectional power semiconductor switch 7 is
reverse-connected in series with the fourth drivable bidirectional power
semiconductor switch 8, the first drivable bidirectional power
semiconductor switch 5 is connected to the capacitor 11, the third
drivable bidirectional power semiconductor switch 7 is connected to the
capacitor 11, the fifth drivable bidirectional power semiconductor switch
9 is directly connected to the fourth drivable bidirectional power
semiconductor switch 8 and directly connected to the junction point
between the first drivable bidirectional power semiconductor switch 5 and
the capacitor 11, and the sixth drivable bidirectional power
semiconductor switch 10 is directly connected to the second drivable
bidirectional power semiconductor switch 6 and directly connected to the
junction point between the third drivable bidirectional power
semiconductor switch 7 and the capacitor 11. Since, in accordance with
FIG. 1, each of the n second switching groups 4.1, . . . 4.n is a
four-terminal network, for n>1 each of the n second switching groups
4.1, . . . 4.n is interlinked with the respective adjacent second
switching group 4.1, . . . 4.n. Furthermore, in accordance with FIG. 1,
the first switching group 1 is connected to the first second switching
group 4.1, and a third switching group 12 and a fourth switching group 13
are provided, each having a first drivable bidirectional power
semiconductor switch 14, 16, a second drivable bidirectional power
semiconductor switch 15, 17, and a capacitor 18, 19 connected to the
first and second drivable bidirectional power semiconductor switches 14,
15, 16, 17, wherein the first and second drivable bidirectional power
semiconductor switches 14, 15, 16, 17 are connected to one another.
Furthermore, in accordance with FIG. 1, the third switching group 12 is
connected to the n-th second switching group 4.n, the fourth switching
group 13 is connected to the n-th second switching group 4.n, and the
third switching group 12 is connected to the fourth switching group 13.
As an alternative, in the case of a second exemplary embodiment of the
converter circuit according to the disclosure according to FIG. 2, P
fifth switching groups 20.1, . . . 20.p are provided, each having a first
and a second drivable bidirectional power semiconductor switch 21, 22,
wherein p>1. Since, in accordance with FIG. 2, each of the p fifth
switching groups 20.1, . . . 20.p is a four-terminal network, for p>1
each of the p fifth switching groups 20.1, . . . 20.p is interlinked with
the respective adjacent fifth switching group 20.1, . . . 20.p. In
accordance with FIG. 2, then the first fifth switching group 20.1 is
connected to the n-th second switching group 4.n, the third switching
group 12 is connected to the p-th fifth switching group 20.p, the fourth
switching group 13 is connected to the p-th fifth switching group 20.p,
and the third switching group 12 is connected to the fourth switching
group 13. The p fifth switching groups 20.1, . . . 20.p advantageously
produce additional redundancy with regard to the drivable bidirectional
power semiconductor switches of the converter circuit according to the
disclosure.

[0023]Given an identical number of switching voltage levels, the converter
circuit according to the disclosure, by means of the n second switching
groups 4.1, . . . , 4.n provided and by means of the third and fourth
switching groups 12,13 and also by means of the p fifth switching groups
20.1, . . . , 20.p and their connections described above, can result in
the number of capacitors 11, 18, 19, 23 of the converter circuit being
kept small and, moreover, in the stored electrical energy of the
converter circuit being reduced. Consequently, the stored electrical
energy of the converter circuit can be kept small overall, whereby the
capacitors 11, 18, 19, 23 of the converter circuit only have to be
designed for a small electrical energy to be stored, that is to say with
regard to their dielectric strength and/or their capacitance. On account
of the resultant small structural size of the capacitors, the converter
circuit requires very little space, with the result that a space-saving
construction such as is required for many applications, for example for
traction applications, is advantageously possible. Moreover, the mounting
and maintenance outlay can also advantageously be kept small as a result
of the small structural size of the capacitors 11, 18, 19, 23.

[0024]If n=1 second switching groups 4.1, . . . 4.n are chosen for example
in the case of the first exemplary embodiment according to FIG. 1, then a
converter circuit for switching nine switching voltage levels with just
three capacitors is achieved. If n=1 second switching groups 4.1, . . .
4.n and p=1 fifth switch groups 20.1, . . . 20.p are chosen for example
in the case of the second exemplary embodiment according to FIG. 2, then
a converter circuit for switching nine switching voltage levels likewise
with only three capacitors is achieved, wherein additional redundancy
with regard to the drivable bidirectional power semiconductor switches of
the converter circuit is advantageously present as a result of the p=1
fifth switching group 20.1, . . . 20.p.

[0025]In accordance with FIG. 1, the first drivable bidirectional power
semiconductor switch 2 of the first switching group 1 is connected to the
junction point between the first drivable bidirectional power
semiconductor switch 5 and the capacitor 11 of the first second switching
group 4.1, and the second power semiconductor switch 3 of the first
switching group 1 is connected to the junction point between the third
drivable bidirectional power semiconductor switch 7 and the capacitor 11
of the first second switching group 4.1. The junction point between the
first drivable bidirectional power semiconductor switch 14 and the second
drivable bidirectional power semiconductor switch 15 of the third
switching group 12 is furthermore connected to the junction point between
the second drivable bidirectional power semiconductor switch 6 and the
sixth drivable bidirectional power semiconductor switch 10 of the n-th
second switching group 4.n. The junction point between the first drivable
bidirectional power semiconductor switch 16 and the second drivable
bidirectional power semiconductor switch 17 of the fourth switching group
13 is furthermore connected to the junction point between the fourth
drivable bidirectional power semiconductor switch 8 and the fifth
drivable bidirectional power semiconductor switch 9 of the n-th second
switching group 4.n. In accordance with FIG. 1, the capacitor 18 of the
third switching group 12 is connected to the capacitor 19 of the fourth
switching group 13.

[0026]In accordance with FIG. 2, the first drivable bidirectional power
semiconductor switch 2 of the first switching group 1 is connected to the
junction point between the first drivable bidirectional power
semiconductor switch 5 and the capacitor 11 of the first second switching
group 1, and the second drivable bidirectional power semiconductor switch
3 of the first switching group 1 is connected to the junction point
between the third drivable bidirectional power semiconductor switch 7 and
the capacitor 11 of the first second switching group 4.1. The first
drivable bidirectional power semiconductor switch 21 of the first fifth
switching group 20.1 is furthermore connected to the junction point
between the second drivable bidirectional power semiconductor switch 6
and the sixth drivable bidirectional power semiconductor switch 10 of the
n-th second switching group 4.n, and the second drivable bidirectional
power semiconductor switch 22 of the first fifth switching group 20.1 is
connected to the junction point between the fourth drivable bidirectional
power semiconductor switch 8 and the fifth drivable bidirectional power
semiconductor switch 9 of the n-th second switching group 4.n. The
junction point between the first drivable bidirectional power
semiconductor switch 14 and the second drivable bidirectional power
semiconductor switch 15 of the third switching group 12 is furthermore
connected to the first drivable bidirectional power semiconductor switch
21 of the p-th fifth switching group 20.p, and the junction point between
the first drivable bidirectional power semiconductor switch 16 and the
second drivable bidirectional power semiconductor switch 17 of the fourth
switching group 13 is connected to the second drivable bidirectional
power semiconductor switch 22 of the p-th fifth switching group 20.p.
Finally, in accordance with FIG. 2, the capacitor 18 of the third
switching group 12 is connected to the capacitor 19 of the fourth
switching group 13.

[0027]FIG. 3 illustrates a third exemplary embodiment of a converter
circuit according to the disclosure. Proceeding from FIG. 1, in FIG. 3
the first drivable bidirectional power semiconductor switch 2 of the
first switching group 1 is connected to the junction point between the
first drivable bidirectional power semiconductor switch 5 and the
capacitor 11 of the first second switching group 4.1, and the second
drivable bidirectional power semiconductor switch 3 of the first
switching group 1 is connected to the junction point between the third
drivable bidirectional power semiconductor switch 7 and the capacitor 11
of the first second switching group 4.1. In contrast to FIG. 1, the
connection of the fifth drivable bidirectional power semiconductor switch
9 to the fourth drivable bidirectional power semiconductor switch 8 in
the case of each second switching group 4.1, . . . 4.n is at the junction
point between the fourth drivable bidirectional power semiconductor
switch 8 and the third drivable bidirectional power semiconductor switch
7, and the connection of the sixth drivable bidirectional power
semiconductor switch 10 to the second drivable bidirectional power
semiconductor switch 6 in the case of each second switching group 4.1, .
. . 4.n is at the junction point between the second drivable
bidirectional power semiconductor switch 6 and the first drivable
bidirectional power semiconductor switch 5. Furthermore, the junction
point between the first drivable bidirectional power semiconductor switch
14 and the second drivable bidirectional power semiconductor switch 15 of
the third switching group 12 is connected to the second drivable
bidirectional power semiconductor switch 6 of the n-th second switching
group 4.n. In addition, the junction point between the first drivable
bidirectional power semiconductor switch 16 and the second drivable
bidirectional power semiconductor switch 17 of the fourth switching group
13 is connected to the fourth drivable bidirectional power semiconductor
switch 8 of the n-th second switching group 4.n, and the capacitor 18 of
the third switching group 12 is connected to the capacitor 19 of the
fourth switching group 13.

[0028]FIG. 4 illustrates a fourth exemplary embodiment of a converter
circuit according to the disclosure. Proceeding from FIG. 2, the
converter circuit in FIG. 4 has each fifth switching group 20.1, . . .
20.p a capacitor 23 connected to the first and second drivable
bidirectional power semiconductor switches 21, 22 of the associated fifth
switching group 20.1, . . . 20.p, wherein the capacitor 23 of the first
fifth switching group 20.1 is connected to the junction point between the
first drivable bidirectional power semiconductor switch 21 of the first
fifth switching group 20.1 and the junction point between the second
drivable bidirectional power semiconductor switch 6 and the sixth
drivable bidirectional power semiconductor switch 10 of n-th second
switching group 4.n. The capacitor 23 of the first fifth switching group
20.1 is additionally connection to the junction point between the second
drivable bidirectional power semiconductor switch 22 of the first fifth
switching group 20.1 and the junction point between the fourth drivable
bidirectional power semiconductor switch 8 and the fifth drivable
bidirectional power semiconductor switch 9 of the n-th second switching
group 20.n. If n=1 second switching groups 4.1, . . . 4.n and p=1 fifth
switching groups 20.1, . . . 20.p are chosen for example in the case of
the fourth exemplary embodiment according to FIG. 4, then a converter
circuit for switching nine switching voltage levels with just four
capacitors is achieved, wherein redundant switching state combinations of
the drivable bidirectional power semiconductor switches, that is to say
that a plurality of switching state combinations produce the same
switching voltage level, can advantageously be achieved by means of the
capacitor 23 of the respective fifth switching groups 20.1, . . . 20.p,
whereby generally the voltage at the respective capacitor 11, 18, 19, 23
of the converter circuit can be stabilized and the drivable bidirectional
power semiconductor switches of the converter circuit generate fewer
losses and can thus be utilized more efficiently.

[0029]FIG. 5 illustrates a fifth exemplary embodiment of a converter
circuit according to the disclosure. Proceeding from FIG. 2, in FIG. 5 in
a manner similar to that in FIG. 3, the first drivable bidirectional
power semiconductor switch 2 of the first switching group 1 is connected
to the junction point between the first drivable bidirectional power
semiconductor switch 5 and the capacitor 11 of the first second switching
group 4.1, and the second drivable bidirectional power semiconductor
switch 3 of the first switching group 1 is connected to the junction
point between the third drivable bidirectional power semiconductor switch
3 and the capacitor 11 of the first second switching group 4.1. In
accordance with FIG. 5, the connection of the fifth drivable
bidirectional power semiconductor switch 9 to the fourth drivable
bidirectional power semiconductor switch 8 in the case of each second
switching group 4.1, . . . 4.n is at the junction point between the
fourth drivable bidirectional power semiconductor switch 8 and the third
drivable bidirectional power semiconductor switch 7. Furthermore, the
connection of the sixth drivable bidirectional power semiconductor switch
10 to the second drivable bidirectional power semiconductor switch 6 in
the case of each second switching group 4.1, . . . 4.n is at the junction
point between the second drivable bidirectional power semiconductor
switch 6 and the first drivable bidirectional power semiconductor switch
5. In addition, the first drivable bidirectional power semiconductor
switch 21 of the first fifth switching group 20.1 is connected to the
second drivable bidirectional power semiconductor switch 6 of the n-th
second switching group 4.n, and the the second drivable bidirectional
power semiconductor switch 22 of the first fifth switching group 20.1 is
connected to the fourth drivable bidirectional power semiconductor switch
8 of the n-th second switching group 4.n. The junction point between the
first drivable bidirectional power semiconductor switch 14 and the second
drivable bidirectional power semiconductor switch 15 of the third
switching group 12 is furthermore connected to the first drivable
bidirectional power semiconductor switch 21 of the p-th fifth switching
group 20.p, and the junction point between the first drivable
bidirectional power semiconductor switch 16 and the second drivable
bidirectional power semiconductor switch 17 of the fourth switching group
13 is connected to the second drivable bidirectional power semiconductor
switch 22 of the p-th fifth switching group 20.p. Finally, the capacitor
18 of the third switching group 12 is connected to the capacitor 19 of
the fourth switching group 13. In accordance with FIG. 2, in the case of
the exemplary embodiment according to FIG. 5, additional redundancy with
regard to the drivable bidirectional power semiconductor switches of the
converter circuit can advantageously be achieved by means of the p fifth
switching groups 20.1, . . . 20.p.

[0030]FIG. 6 illustrates a sixth exemplary embodiment of a converter
circuit according to the disclosure. Proceeding from FIG. 5, in FIG. 6
each fifth switching group 20.1, . . . 20.p has a capacitor 23 connected
to the first and second drivable bidirectional power semiconductor
switches 21, 22 of the associated fifth switching group 20.1, . . . 20.p,
wherein the capacitor 23 of the first fifth switching group 20.1 is
connected to the junction point between the first drivable bidirectional
power semiconductor switch 21 of the first fifth switching group 20.1 and
the second drivable bidirectional power semiconductor switch 6 of the
n-th second switching group 4.n. Furthermore, the capacitor 23 of the
first fifth switching group 20.1 is connected to the junction point
between the second drivable bidirectional power semiconductor switch 22
of the first fifth switching group 20.1 and the fourth drivable
bidirectional power semiconductor switch 8 of the n-th second switching
group 4.n. If n=1 second switching groups 4.1, . . . 4.n and p=1 fifth
switching groups 20.1, . . . 20.p are chosen for example in the case of
the sixth exemplary embodiment according to FIG. 6, then a converter
circuit for switching nine switching voltage levels with just four
capacitors is achieved, wherein redundant switching state combinations of
the drivable bidirectional power semiconductor switches, that is to say
that a plurality of switching state combinations produce the same
switching voltage level, can advantageously be achieved by means of the
capacitor 23 of the respective fifth switching groups 20.1, . . . 20.p,
whereby generally the voltage at the respective capacitor 11, 18, 19, 23
of the converter circuit can be stabilized and the drivable bidirectional
power semiconductor switches of the converter circuit generate fewer
losses and can thus be utilized more efficiently.

[0031]As a further variant with respect to FIG. 5 and in contrast to FIG.
6, it is also conceivable for only the first fifth switching group 20.1
to have a capacitor 23 connected to the first and second drivable
bidirectional power semiconductor switches 21, 22 of first fifth
switching group 20.1, wherein the capacitor 23 of the first fifth
switching group 20.1 is connected to the junction point between the first
drivable bidirectional power semiconductor switch 21 of the first fifth
switching group 20.1 and the second drivable bidirectional power
semiconductor switch 6 of the n-th second switching group 4.n.
Furthermore, the capacitor 23 of the first fifth switching group 20.1 is
connected to the junction point between the second drivable bidirectional
power semiconductor switch 22 of the first fifth switching group 20.1 and
the fourth drivable bidirectional power semiconductor switch 8 of the
n-th second switching group 4.n. For n=1 second switching groups 4.1, . .
. 4.n and p=2 fifth switching groups 20.1, . . . 20.p, wherein the first
fifth switching groups 20.1 have the capacitor 23 and the second fifth
switching groups 20.2 then have no capacitor 23, a converter circuit for
switching nine switching voltage levels with just four capacitors is
achieved, wherein redundant switching state combinations of the drivable
bidirectional power semiconductor switches, that is to say that a
plurality of switching state combinations produce the same switching
voltage level, can advantageously be achieved by means of the capacitor
23 of the respective fifth switching groups 20.1, . . . 20.p, whereby
generally the voltage at the respective capacitor 11, 18, 19, 23 of the
converter circuit can be stabilized and the drivable bidirectional power
semiconductor switches of the converter circuit generate fewer losses and
can thus be utilized more efficiently.

[0032]As a further variant with respect to FIG. 5 and in contrast to FIG.
6, it is likewise conceivable for the first fifth switching group 20.1
and at least one further fifth switching group 20.2, . . . 20.p each to
have a capacitor 23 connected to the first and second drivable
bidirectional power semiconductor switches 21, 22 of the associated fifth
switching group 20.1, 20.2, . . . , 20.p, wherein the capacitor 23 of the
first fifth switching group 20.1 is connected to the junction point
between the first drivable bidirectional power semiconductor switch 21 of
the first fifth switching group 20.1 and the second drivable
bidirectional power semiconductor switch 6 of the n-th second switching
group 4.n. Furthermore, the capacitor 23 of the first fifth switching
group 20.1 is connected to the junction point between the second drivable
bidirectional power semiconductor switch 22 of the first fifth switching
group 20.1 and the fourth drivable bidirectional power semiconductor
switch 8 of the n-th second switching group 4.n.

[0033]In all the exemplary embodiments it is conceivable for the first,
second, third, fourth, fifth and sixth drivable bidirectional power
semiconductor switches 5, 6, 7, 8, 9, 10 of each second switching group
4.1, . . . 4.n preferably each to have at least two drivable
bidirectional switching elements, wherein the drivable bidirectional
switching elements are connected in series. It is thus advantageously
possible to increase the voltage to be switched at the respective
drivable bidirectional power semiconductor switches 5, 6, 7, 8, 9, 10.
Furthermore, it is also possible for the first and second drivable
bidirectional power semiconductor switches 21, 22 of each fifth switching
group 20.1, . . . 20.p each to have at least two drivable bidirectional
switching elements, wherein the drivable bidirectional switching elements
are connected in series. In this case, too, it is possible to increase
the voltage to be switched at the respective drivable bidirectional power
semiconductor switch 21, 22. Furthermore, it is also possible for the
first and second drivable bidirectional power semiconductor switches 14,
15 of the third switching group 12 and the first and second drivable
bidirectional power semiconductor switches 16, 17 of the fourth switching
group 13 each to have at least two drivable bidirectional switching
elements, wherein the drivable bidirectional switching elements are
connected in series. In that case, too, it is possible advantageously to
increase the voltage to be switched at the respective drivable
bidirectional power semiconductor switches 14, 15, 16, 17. Accordingly,
any desired number of drivable bidirectional switching elements is
possible for each drivable bidirectional power semiconductor switch 5, 6,
7, 8, 9, 10, 14, 15, 16, 17, 21, 22 with regard to the exemplary
embodiments according to FIG. 1 to FIG. 6. In this respect, FIG. 7
illustrates a seventh exemplary embodiment of a converter circuit
according to the disclosure, wherein by way of example n=1 second
switching group 4.1, . . . 4.n is provided in accordance with FIG. 3 and
the first, second, third, fourth, fifth and sixth drivable bidirectional
power semiconductor switches 5, 6, 7, 8, 9, 10 of the single second
switching group 4.1 each have two drivable bidirectional switching
elements and the first and second drivable bidirectional power
semiconductor switches 14, 15, 16, 17 of the third and fourth switching
groups 12, 13 each have three drivable bidirectional switching elements.

[0034]The respective drivable bidirectional switching element of each
drivable bidirectional power semiconductor switch of the converter
circuit can be formed for example by a bipolar transistor having a drive
electrode arranged in insulated fashion (IGBT--Insulated Gate Bipolar
Transistor) and by a diode reverse-connected in parallel therewith. In
order to be able to switch a high voltage at the capacitors 18, 19 of the
third and fourth switching groups 12, 13, the drivable bidirectional
switching element of the first and second drivable bidirectional power
semiconductor switches 14, 15, 16, 17 of the third and fourth switching
groups 12, 13 can be formed by an integrated thyristor having a
commutated drive electrode (integrated gate commutated thyristor (IGCT))
and by a diode reverse-connected in parallel therewith.

[0035]Overall, the converter circuit according to the disclosure for
switching a large number of switching voltage levels thus represents a
solution which is characterized by a small stored electrical energy
during its operation and by a space-saving construction and is therefore
uncomplicated, robust and not very susceptible to interference.

[0036]It will be appreciated by those skilled in the art that the present
invention can be embodied in other specific forms without departing from
the spirit or essential characteristics thereof. The presently disclosed
embodiments are therefore considered in all respects to be illustrative
and not restricted. The scope of the invention is indicated by the
appended claims rather than the foregoing description and all changes
that come within the meaning and range and equivalence thereof are
intended to be embraced therein.

List of Reference Symbols

[0037]1 First switching group [0038]2 First drivable bidirectional power
semiconductor switch of the first switching group [0039]3 Second drivable
bidirectional power semiconductor switch of the first switching group
[0040]4.1, 4.n Second switching groups [0041]5 First drivable
bidirectional power semiconductor switch of the second switching groups
[0042]6 Second drivable bidirectional power semiconductor switch of the
second switching groups [0043]7 Third drivable bidirectional power
semiconductor switch of the second switching groups [0044]8 Fourth
drivable bidirectional power semiconductor switch of the second switching
groups [0045]9 Fifth drivable bidirectional power semiconductor switch of
the second switching groups [0046]10 Sixth drivable bidirectional power
semiconductor switch of the second switching groups [0047]11 Capacitor of
the second switching groups [0048]12 Third switching group [0049]13
Fourth switching group [0050]14 First drivable bidirectional power
semiconductor switch of the third switching group [0051]15 Second
drivable bidirectional power semiconductor switch of the third switching
group [0052]16 First drivable bidirectional power semiconductor switch of
the fourth switching group [0053]17 Second drivable bidirectional power
semiconductor switch of the fourth switching group [0054]18 Capacitor of
the of the third switching group [0055]19 Capacitor of the fourth
switching group [0056]20.1, . . . 20.p Fifth switching groups [0057]21
First drivable bidirectional power semiconductor switch of the fifth
switching groups [0058]22 Second drivable bidirectional power
semiconductor switch of the fifth switching groups [0059]23 Capacitor of
the fifth switching group